Dental amalgam may cause mercury poisoning in genetically susceptible children, according to a report published February 1 in the peer-reviewed journal, Biometals. Ironically, this finding arises from several reanalyses of a key clinical trial that is cited by the U.S. Food and Drug Administration (FDA) as evidence for the safety of amalgam.

The report, entitled, "New science challenges old notion that mercury dental amalgam is safe," identifies several common genetic variants that convey susceptibility to mercury poisoning. The report asserts that mercury vapor from dental amalgam appears to contribute significantly to mercury body burden, and that this exposure appears sufficient to cause harm to susceptible individuals. Finally, the report notes that many Americans with amalgams are exposed to unsafe levels of mercury vapor according to well-established regulatory standards.

Dental amalgam, the material used for "silver" fillings, contains 50% mercury. Once thought inert, the FDA and the American Dental Association (ADA) now admit that amalgam fillings release mercury vapor. The debate is over whether these levels are harmful.

The FDA and the ADA base their claims of safety largely on the results of two randomized, controlled, clinical trials on amalgam, which are known as the Children's Amalgam Trials. The initial results, reported in 2006 in the Journal of the American Medical Association, showed no significant difference between the children who received amalgam fillings and those who received resin composite fillings, in terms of group-average measures of brain function.

Contrary results were observed in 2011 by an independent team that reanalyzed in more detail the longer of the two clinical trials. The investigators divided the amalgam group into high, medium, and low amalgam exposure. This refinement revealed biomarkers of known metabolic harm, called porphyrins, that were associated with higher levels of amalgam. A further reanalysis found that boys who had a common genetic variant, in addition to more exposure to mercury, experienced measurable brain deficits, particularly attention deficit.

From 2011 to 2013, a total of four separate reanalyses have revealed several measures of biological harm to children in a clinical trial lasting seven years. If left unaddressed for several decades, children will continue to be harmed from exposure to mercury in dental amalgams. According to lead author, Kristin Homme, "We're concerned because mercury appears to be the most biochemically plausible explanation for many mysterious conditions, from developmental disorders to neurodegenerative conditions."

According to the report, six common genes have been identified that convey susceptibility to mercury, and many more are likely. These findings help explain the amalgam controversy -- why some people seem to be harmed by their mercury fillings, while others appear to be fine, and why amalgam studies have shown inconsistent results, leading authorities to presume the product is safe.

While the FDA asserts that amalgam illness is anecdotal, dozens of injured consumers have testified at FDA meetings in 2006, 2010, and 2011, yet none have been investigated by the agency. Stacy Case, for example, a telegenic Nashville news anchor who testified in 2011, was diagnosed with Multiple Sclerosis. When she learned that her mercury levels were high, she had her amalgams removed "safely", and after several years her symptoms disappeared.

In 2010, at the urging of its scientific advisory panel, the FDA agreed to review its amalgam rule based on current science. The agency announced its intention to complete its review by 2011, yet they have been silent ever since.